The present invention relates to a gas inlet for different reactant gases which flow into reaction vessels with high flow velocity, and having supply lines whose cross sections are substantially smaller than that of the reaction vessel.
Gas inlets of this kind are needed, by way of illustration in MOCVD ( metal oxide chemical vapor deposition) reactors, but also in other reactors for the production of semi-conductors, whereby the general problem is that one or several gas flows led in via a supply line having a relatively small cross section should be widened to a large cross section as homogeneously as possible and with no dead volume. This is particularly significant if as "sharp" as possible boundaries are to be produced between the films by switching the gas flows.
An object of present invention is to improve a gas inlet for a majority of reactant gases into reaction vessels in such a manner that one or more gas flows can be widened to a relatively large cross section as homogeneously as possible with no dead volume.
An inventive feature is that the gas inlet has a part, the interior contour of which is conicoidal in shape, the cross section of which is adapted to the cross section of the reaction vessel and which is arranged at one end of the reaction vessel through which flow occurs. The individual supply lines end at approximately the focal point of the part having a conicoidal interior contour, whereby the gas exit openings of the supply lines are directed at the vertex of the conicoidal part.
Thus, the "thin" gas jet issuing with high velocity from the gas exit openings of the supply lines is widened homogeneously and with no dead volume with reflection off the conicoidal interior contour. An star-shaped arrangment of the supply lines permits the introduction of several types of gas (simultaneously and/or serially) without disturbing the homogeneity of the widened gas flow.
For practical purposes a more than sufficient homogeneity of the widened gas jet is yielded if the interior contour of the conicoidal part, i.e. the conicoidal shape, is approximated by a hemisphere.
As result of gas exit openings of the supply line atomization is achieved, and thereby further homogeneity of the gas flow via the cross section of the reactor is obtained.